IVGCVSW-6310 Update ICustomAllocator and add GetDefaultAllocator function to backends

Signed-off-by: Francis Murtagh <francis.murtagh@arm.com>
Change-Id: If2879e8a82692285e7fa3f4d09abd608ca28de12
diff --git a/include/armnn/backends/IBackendInternal.hpp b/include/armnn/backends/IBackendInternal.hpp
index f4fe678..7500e35 100644
--- a/include/armnn/backends/IBackendInternal.hpp
+++ b/include/armnn/backends/IBackendInternal.hpp
@@ -13,12 +13,12 @@
 #include <SubgraphView.hpp>
 #include <optimizations/Optimization.hpp>
 
-#include "IBackendContext.hpp"
-#include "armnn/backends/profiling/IBackendProfiling.hpp"
-#include "armnn/backends/profiling/IBackendProfilingContext.hpp"
-#include "IMemoryManager.hpp"
-#include "ITensorHandleFactory.hpp"
-#include "OptimizationViews.hpp"
+#include <armnn/backends/IBackendContext.hpp>
+#include <armnn/backends/IMemoryManager.hpp>
+#include <armnn/backends/ITensorHandleFactory.hpp>
+#include <armnn/backends/OptimizationViews.hpp>
+#include <armnn/backends/profiling/IBackendProfiling.hpp>
+#include <armnn/backends/profiling/IBackendProfilingContext.hpp>
 
 #include <vector>
 #include <memory>
@@ -198,6 +198,14 @@
         }
         return false;
     }
+
+    /// Returns the default memory allocator for the backend
+    ///
+    /// \return - Returns unique pointer to the Default Allocator of the Backend
+    virtual std::unique_ptr<ICustomAllocator> GetDefaultAllocator() const
+    {
+        throw armnn::Exception("GetDefaultAllocator: Function has not been implemented in backend.");
+    }
 };
 
 using IBackendInternalUniquePtr = std::unique_ptr<IBackendInternal>;